This invention relates to a valve assembly having at least one passageway through a bushing through which a fluid can be injected to wash contaminants away from the stem seals. In particular, it relates to a valve assembly for controlling the flow of brine.
Ethylene and propylene gases, produced by cracking crude oil, are often stored in underground salt caverns. To force the gases out of the caverns, brine, which will not dissolve the salt, is pumped into the caverns. Pneumatically operated gate valves are used to control the flow of brine into and out of these caverns. Abrasive salt crystals from the brine tend to adhere to the valve stem. They increase the friction on the stem, making it more difficult to operate the valve, and abrade the stem seals, causing the valve to fail. When a valve becomes so clogged that it can not be opened or closed pneumatically, a worker must be sent into the field to close the valve. This is done by physically pulling the stem up using a tool, a demanding task that can damage the piston retainers on the valve.